Study Claims Complex Life on Earth Evolved a Billion Years Earlier Than We Thought

When life began on Earth, it took billions of years for it to reach even the minimum requirements for complexity and become multicellular. Now, researchers from China are claiming that it didn't take quite as long as we thought, as they have found fossils of complex organisms that evolved more than 1.5 billion years ago, nearly a billion years earlier than scientists originally believed.

According to the general scientific consensus, life first emerged on Earth as single-celled organisms from the primordial soup approximately 3.8 billion years ago, and remained primitive for billions of years after that. Scientists have often called this period the "boring billion," because evolution and the environment appear to be stagnant during this time.

But at some point, these unicellular organisms evolved into complex eukaryotes, which gave rise to all of the recognizable life on Earth today. Scientists have estimated that this occurred about half a billion years ago, but now, a team of researchers has discovered fossils in the Yanshan region of Hebei province in China that seem to indicate our numbers are off. They found 167 fossils, a third of which were one of four regular shapes, which is a sign of complexity. Taken together, they are "compelling evidence for the early evolution of organisms large enough to be visible with the naked eye."

"Our discovery pushes back nearly one billion years the appearance of macroscopic, multi-cellular eukaryotes compared to previous research," said Maoyan Zhu, a professor at the Nanjing Institute of Geology and Palaeontology. "This totally renews current knowledge on the early history of life."

The researchers concluded in their paper, published in Nature Communications, that the fossils record a "modest diversity of macroscopic multicellular eukaryotic organisms" that lived in oceans in the Mesozoic era, originally thought to be part of the "boring billion." This is a huge discovery, and one that is sure to be controversial, as their peers have already started praising the study as revolutionary or dismissing it as inaccurate. Phil Donoghue, a professor of palaeobiology at the University of Bristol, described the discovery as a "big deal."

"They are not the oldest eukaryotes, but they are certainly the oldest demonstrably multicellular eukaryotes," he said.

Other researchers, however, claimed that there wasn't sufficient detail in the study to come to any conclusion, and that it's just as likely the fossils had recorded colonies of bacteria.

"There is nothing here to suggest that the specimens are eukaryotic, as opposed to bacterial," said Jonathan Antcliffe, a senior researcher in the University of Oxford's department of zoology.

If found to be true, however, this could have a huge impact on our knowledge of the earliest history of life, as well as Earth's environment during that time period. If these organisms did arise 1.5 billion years ago, that is strong evidence that the oxygen levels were much higher than we thought. As a result, the "boring billion"--which has been, according to the researchers, "caricatured misleadingly as a 'boring billion' year interval of evolutionary stability"--may have been much more dynamic than it is given credit for.